1. Field of the Invention
The present invention relates to a wafer processing method for dividing a wafer into individual devices along a plurality of crossing division lines formed on the front side of the wafer, the individual devices being respectively formed in a plurality of separate regions defined by the division lines.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby define a plurality of separate regions where a plurality of devices such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along the division lines to thereby divide the regions where the devices are formed from each other, thus obtaining the individual devices. Cutting of the semiconductor wafer along the division lines is usually performed by using a cutting apparatus called a dicing saw. This cutting apparatus includes a chuck table for holding a workpiece, cutting means having a cutting blade for cutting the workpiece held on the chuck table, and feeding means for relatively moving the chuck table and the cutting means. By feeding the chuck table holding the workpiece as rotating the cutting blade, the wafer is cut along each division line.
However, when the wafer is cut by the cutting blade of the cutting apparatus mentioned above, chipping is apt to occur in the periphery of each device chip divided from the wafer, causing a reduction in die strength of each device chip. To solve such a problem, there has been proposed a method including the steps of forming a resist film on the back side of a wafer, exposing to light the region of the resist film corresponding to each division line of the wafer, thereby removing this region by development, and then etching the wafer from the resist film side along the division lines by plasma etching or the like, thereby dividing the wafer along the division lines (see Japanese Patent Laid-open No. 2006-120834, for example).
The above method of dividing the wafer along the division lines by using plasma etching has the following merits. Unlike the cutting by the use of a cutting blade, no chipping occurs along a division groove formed by the plasma etching, so that the die strength of each device can be improved. Further, even when the diameter of the wafer becomes as large as 450 mm or 600 mm, all of the division lines can be etched at a time to divide the wafer into the individual devices, thereby improving the productivity.